The England defender could be set for a January exit after growing increasingly frustrated with life at the Reebok Stadium.
Saturday's 2-0 loss to Sunderland was a fifth straight Premier League home defeat and 25-year-old Cahill, who has also been linked with Arsenal, said: "A few of the lads, myself included, need to have a look and question themselves over whether they are doing enough.
"You can maybe afford to carry one player but you cannot afford to carry a handful and it has been different players in different games.
"When you are under pressure, there is only so much you can head out and defend. It is difficult because I was out there (against Sunderland) thinking, 'Why are we under so much pressure?'
"We were defending all the time. We have to sort it out."